The terms K2 and Spice refer to any number of commercial products usually sold as legal marijuana. These products contain dangerous synthetic cannabinoid (SCBs) that are presumed to possess psychoactive properties similar to ?9-tetrahydrocannabinol (?9-THC), the natural cannabinoid found in marijuana. ?9-THC and SCBs both produce psychotropic actions by activating CB1 cannabinoid receptors (CB1Rs) in the CNS. However, SCBs are a chemically diverse group of compounds that are structurally distinct from ?9-THC, and thus detection of their use is difficult and has led to widespread abuse. Medical use of marijuana and ?9-THC has been shown to be safe. In marked contrast, no information is known concerning the safety or efficacy of any SCB found in K2, and reports suggest that many clinical effects of K2 products are distinct from those produced by marijuana and may present health risks. In this regard, our preliminary analysis of urine samples from SCB users by LC-MS/MS suggests that levels of SCB metabolites correlate with clinical symptoms that may be life threatening. Furthermore, we reported that several hydroxylated metabolites of SCBs retain high affinity and activity at CB1R and CB2Rs, and dramatically increase acute effects of parent SCBs. Therefore, in an individual user, the physiological effects of SCBs may represent an entourage effect caused 1) by the distinct blend of SCBs in a given product, and 2) further influenced by the individual's metabolic capacity to transform SCBs into distinct Phase I and II active metabolites. Thus, it is important to define the metabolic profile of SCBs in humans and their biological activity at CB1Rs and CB2Rs. The goal of this project is to elucidate the biodisposition, biotransformation, and biological activity of SCBs and their metabolites at CB1Rs and CB2Rs in humans, and correlate these findings with acute and chronic adverse effects in mice. We will test the hypothesis that in vivo hydroxylation of SCBs by cytochromes P450 (CYPs) and subsequent conjugation by UDP-glucuronosyltransferases (UGTs) and sulfotransferases (SULTs) produces a complex mixture of high affinity CB1R and CB2R agonists, antagonists, and inverse agonists. These metabolites acting in concert with parent SCBs produce the distinct pharmacologic effects and toxicity of SCBs in humans. Our interdisciplinary team will explore this hypothesis by four Specific Aims. Aim 1 will employ LC-MS/MS to identify in human urine the primary and secondary metabolites of 9 high priority SCBs abused in K2 products. Clinical symptom profiles will also be collected for each patient. Experiments in Aim 2 will characterize the human Phase I and II enzymes responsible for the in vitro metabolism of SCBs. In Aim 3, SCBs and their metabolites will be examined for the ability to bind to and activate human CB1Rs and CB2Rs. Finally, studies in Aim 4 will determine the pharmacokinetic profile of SCBs and determine if these compounds and their metabolites elicit cannabimimetic effects in mice. This collaborative translational project will provide information concerning the metabolism, pharmacology and toxicology of SCBs to identify likely health risks to the public.